A multicenter collaborative randomized clinical comparison of 5-fluorocytosine-amphotericin B with amphotericin B in cryptococcal meningitis has found that six weeks of the combination drug is at least as good as ten weeks of the single drug. Mechanism of action 5-fluorocytosine on Candida albicans was found to be inhibition of the enzyme, thymidylate synthetase. Serotype D Cryptococcus neoformans was found to be much more prevalent in Europe than in the U.S.A.